Process for the production of monoalkyltin thihalides

ABSTRACT

The present invention is directed to a process for the production of monoalkylin trihalides of the formula RSnX3 wherein R-alkyl or cycloalkyl and X—Cl, Br or I involving a redistribution reaction between tetraorganotins, triorganotin halides or diorganotin halides and tin tetrahalides, said process comprising contacting tetra-(R4Sn), tri-(R3SnX) or diorganotin halides (R2SnX2) with SnX4 to afford said monoorganotin trihalides in the presence of at least one transition metal complex, said complex comprising at least one transition metal M, selected from Group VIII of the periodic Table of elements, at least one monodentate ligand or bidentate ligand, L, L′, or L″, and optionally one or more anions, X, of an organic or inorganic acid, as a catalyst or catalyst precursor.

[0001] The present invention concerns a transition metal-catalyzed process for the production of monoalkyltin trihalides involving a redistribution reaction between tetraorganotins, triorganotin halides or diorganotin halides and tin tetrahalides.

[0002] Monoalkyltin trichlorides can be prepared industrially from tetraalkyltins and SnCl₄ according to the stoichiometry of eq. 1 (Neumann, W. P.; Burkhardt, G. Liebigs Ann. Chem. 1963, 663, 11).

R₄Sn+2 SnCl₄→2 RSnCl₂+R₂SnCl₂   (1)

R₄Sn+3 SnCl₄→4 RSnCl₃   (2)

R₂SnCl₂+SnCl₄→2 RSnCl₃   (3)

(R=alkyl or cycloalkyl)

[0003] This process was further improved by M&T chemicals (Natoli, J. G., U.S. Pat. No. 3,432,531, 1969; Larkin, W. A.; Bouchoux, J. W., U.S. Pat. No. 3,931,264, 1976). In this process substantial amounts of dialkyltin dichloride are formed as by-product (typically around 33%).

[0004] The reason that the process according to eq. 1 is often used and not that of eq. 2, is that eq. 3 does not proceed under mild conditions for longer alkyl groups. Eq. 3 would be the last step in a process according to eq. 2.

[0005] Nothwithstanding the above remarks, Neumann (U.S. Pat. No. 3,459,779, 1969) has described the redistribution reaction of dialkyltin halides with SnCl₄ in POCl₃/P₂O₅ to produce monoalkyltin trichlorides. Also Langer et al. reported the formation of MeSnCl₃ from dimethyltin dichloride and tin tetrachloride in dimethylsulfoxide (DMSO) (Tetrahedron Lett., 1967, 1, 43-47; U.S. Pat. No. 3,454,610, 1969, to Dow Chemical Co.). Also the redistribution of dialkyltin dihalides, trialkyltin halides or tetraalkyltins with tin tetrahalide catalyzed by quarternary ammonium salts at temperatures above 150° C. has been reported (Kugele, T. G.; Parker, D. H., U.S. Pat. No. 3,862,198, 1975) and more recently, redistribution reactions of organotins catalyzed by SnF₂ were claimed by Buschhoff et al. (U.S. Pat. No. 4,604,475, 1986, to Schering A. G.).

[0006] All the processes described above generally use harsh reaction conditions and yields are often less than desirable.

[0007] It is therefore an object of the current invention to provide for a catalytic process for the production of monoorganotin trihalides from tetraalkyltins or polyalkyltin halides and tin tetrahalide that can be operated under mild conditions (T<150° C., p≦5 bar) and which affords the product in high yield (>60% based on Sn).

[0008] It is also an object of the current invention to make use of transition metal complexes as pre)catalyst as opposed to previously reported catalysts.

[0009] In its broadest form the present invention comprises a process for the production of monoalkyltin trihalides of the formula RSaX₃, wherein R=alkyl or cycloalkyl and X═Cl, Br or I, involving a redistribution reaction between tetraorganotins, triorganotin halides or diorganotin halides and tin tetrahalides, said process comprising contacting tetra-(R₄Sn), tri-(R₃SnX) or diorganiotin halides (R₂SnX₂) with SnX₄ to afford said monoorganotin trihalides in the presence of at least one transition metal complex, said complex comprising at least one transition metal, M, selected from Group VIII of the periodic Table of elements, at least one monodentate ligand or bidentate ligand, L or L′, and optionally one or more anions, X, of an organic or inorganic acid, as a catalyst or catalyst precursor.

[0010] According to one embodiment of the invention, the catalyst is based on the use of a complex having the formula

L′MX₂   (I)

[0011] wherein L′ is a bidentate ligand, or

L₂MX₂   (II)

[0012] wherein L is a monodentate ligand, or

L₄M   (III),

[0013] wherein L is a monodentate ligand.

[0014] According to another embodiment, the said complex is:

[L″M(μ−X)]₂   (IV)

[0015] wherein L″=a cyclometallated bidentate optionally substituted o-(diarylphosphino)benz-yl ligand. Catalysts of type (IV) have been applied for the Heck-vinylation of aryl halides (EP 725049 A1).

[0016] The metal to be used is a Group VIII metal, and preferred metals are Pt, Pd and/or Ni. The anions may be of organic and/or inorganic nature. It is preferred to use Cl, Br, I, acetate, triflate or tosylate anions.

[0017] The current invention thus involves the use of transition metal complexes according to formula (I), (II), (III), or (IV) as a (pre-)catalyst in the redistribution reaction of tetra-(R₄Sn), tri-(R₃SnX) or diorganotin halides (R₂SnX₂) with SnX₄ to afford monoorganotin trihalides (RSnX₃; R=alkyl or cycloalkyl; X═Cl, Br or I).

[0018] In a preferred embodiment of the invention L in formula (II) or (III) is selected from phosphine, alkene, amine, organic sulfide, nitrile and imidazoline-2-ylidene. L′ is selected from diphosphine, dialkene, diamine and bis(imidazoline-2-ylidene) ligands, preferably optionally substituted o-{di(2-tolyl)phosphino}benzyl. More in particular L is triphenylphosphine or L′=N,N,N′,N′-tetramethylethylenediamine (TMEDA), M is Pd or Pt and for catalyst (I), X is Cl.

[0019] The catalyzed redistribution reaction concerns the redistribution of Bu₂SnCl₂ or Bu₄Sn with SnCl₄ to afford BuSnCl₃. The use of (pre)catalysts according to formula (I), (II), (III) and (IV) allows the formation of BuSnCl₃ from redistribution of Bu₂SnCl₂ or Bu₄Sn with SnCl₄ under mild reaction conditions (T≦150° C., p≦1 bar) in less than 24 hours and better than 70% yield (based on Sn).

[0020] The group R is preferably defined as an alkyl (linear or branched), cycloaryl or aryl, having from 1 to 12 C-atoms. Preferably methyl, n-butyl or n-hexyl are used.

[0021] The reaction can be carried out with or without a solvent. In general inert organic and aprotic solvents are preferred, especially aromatic solvents, chloroaromatics, alkanes, dialkylacetamides, N-alkylpyrolidones, dialkylamides of aliphatic carboxylic acids and organic nitriles. In particular toluene, o-xylene, 1,2-dichlorobenzene and n-octane were found to be appropriate solvents.

[0022] In a specific embodiment of the invention the concentration of the tin reagents employed falls within the range of 0.01 to 5, more preferred 0.1-2.0 M

[0023] The catalyst loading based on the total amount of Sn used can be <5% and even <0.1%. The catalyst is preferably employed in the concentration range 5·10⁻⁴-0.1 M.

[0024] In one specific example, which employed PtCl₂(PPh₃)₂ as catalyst (or catalyst precursor) in toluene at a reaction temperature of 85° C., the yield of BuSnCl₃ was found to be as high as 92% (based on Sn). SnCl₂ was the sole tin-containing by-product.

[0025] In another preferred embodiment of the invention the catalyzed redistribution reaction concerns redistribution between R₂SnCl₂ or R₄Sn (R is Me, Et, propyl, hexyl, more preferably Me and n-hexyl) and SnCl₄ to afford RSnCl₃. For R=Me and n-hexyl, the monoalkyltin trichloride was obtained starting from R₂SnCl₂ and SnCl₄ in 87 and 67% yield, repectively, whereas in the blank experiment (no catalyst added) only unreacted starting materials were recovered.

[0026] The invention is now further demonstrated by the following examples.

EXAMPLES Preparation of BuSnCl₂ from Bu₂SnCl₂ and SnCl₄

[0027] Bu₂SnCl₂ was either dissolved in the solvent or used as such. SnCl₄ was added followed by the catalyst. The reaction mixture was stirred for 12 h at 110° C. Filtration of the reaction mixture gave a slightly yellow solution which was analyzed by ¹¹⁹Sn NMR using SuMe₄ as external standard. After evaporation of the solvent, butyltin trichloride was obtained as a colorless liquid by vacuum distillation (90° C./11 mmHg) and analyzed by ¹H, ¹³C{¹H} and ¹¹⁹Sn{¹H} NMR spectroscopy. The solid material obtained from the filtration was washed with toluene (3×20 mL) and dried in vacuo to give an off-white solid which was identified as SnCl₂ by ¹¹⁹Sn NMR (δ=−235.1 in acetone-d₆) and/or elemental analysis. The results of the different experiments are presented in Table 1.

[0028] In one typical experiment, 373 g (1.32 mol, 80%) of BuSnCl₃ and 44.5 g (0.23 mol, 14%) of SnCl₂ were obtained starting from Bu₂SnCl₂ (252 g, 0.83 mol) in toluene (500 mL), SnCl₄ (215 g, 0.83 mol) and PtCl₂(PPh₃)₂ (215 mg, 0.27 mmol) as catalyst following the above procedure. Elemental analysis of SnCl₂: Cl, 37.0%; Sn, 61.23 %. SnCl₂ requires: Cl, 37.4%; Sn, 62.60%. TABLE 1 Results of the reaction of BU₂SUCl₂ with SnCh (1:1 molar ratio) in the presence of several catalysts.^(a) Yield T [Catalyst] of Selectivity Entry Catalyst (° C.) (mol %)^(b) Solvent^(c) BnSnCl₃ (%)^(d) (%)^(e) 1 Pd(PPh₃)₄ 110 5 no solvent   60 (25) n.d. 2 PdCl₂(PPh₃)₂ 110 1.10 no solvent   64 n.d. 3 PdCl₂(TMEDA) 110 5 no solvent   72 (70) n.d. 4 PtCl₂(PPh₃)₂ 110 0.1 no solvent   62 n.d. 5 PtCl₂(PPh₃)₂ 110 1 toluene   72 n.d. 6 PtCl₂(PPh₃)₂ 85 0.1 toluene   92^(f) 93^(f) 7 PtCl₂(PPh₃)₂ 110 0.1 toluene   84 (80) 87 8 PtCl₂(PPh₃)₂ 130 0.1 toluene   85 86 9 PtCl₂(PPh₃)₂ 110 0.03 toluene n.d. n.d. (80) 10 PtCl₂(PPh₃)₂ 110 0.1 o-xylene   70 79 11 PtCl₂(PPh₃)₂ 110 0.1 1,2-   85 83 dichlorobenzene 12 PtCl₂(PPh₃)₂ 110 0.1 n-octane   76 89

Preparation of MeSnCl₃ from Me₂SnCl₂ and SnCl₄

[0029] In this typical experiment, 3.40 g (14.1 mmol, 87%) of MeSnCl₃ was obtained starting from Me₂SnCl₂ (1.80 g, 8.3 mmol) in toluene (5 mL), SnCl₄ (1.0 mL, 8.3 mmol) and PtCl₂(PPh₃)₂ (6.5 mg, 8.2 μmol) as catalyst following the above procedure for preparation of BuSnCl₃. After filtration volatiles were removed in vacuo (1 mm Hg) to afford the product as a white solid. No SnCl₂ formation was observed.

Preparation of (n-C₆H₁₃)SnCl₃ from (n-C₆H₁₃)₂SnCl₂ and SnCl₄

[0030] In this typical experiment, 1.15 g (3.70 mmol, 67%) of (n-C₆H₁₃)SnCl₃ was obtained starting from (n-C₆H₁₃)₂SnCl₂ (1.0 g, 2.78 mmol) in toluene (10 mL), SnCl₄ (0.72 g, 2.78 mmol) and PtCl₂(PPh₃)₂ (23 mg, 27.8 μmol) as catalyst following the above procedure for preparation of BuSnCl₃. After filtration volatiles were removed in vacuo (2 mm Hg) and the remaining liquid was vacuum-transferred (ca 200° C., 1-2 mm Hg). SnCl₂ (0.23 g, 1.2 mmol, 21%) was isolated as side-product.

Preparation of BuSnCl₃ from Bu₄Sn and SnCl₄

[0031] In this typical procedure, SnCl₄ (11.15 g, 0.043 mol) was dissolved in toluene (10 mL). Next, Bu₄Sn (4.96 g, 0.0143 mol) was added and reaction mixture was stirred for 2 h at 110° C. After cooling of the reaction mixture to room temperature, the catalyst PtCl₂(PPh₃)₂ (3.8 mg, 4.8 μmol) was added and the reaction mixture was stirred for another 12 h at 110° C. Filtration of the reaction mixture gave a slightly yellow solution which was analyzed by ¹¹⁹Sn NMR using SnMe₁ as external standard. After evaporation of volatiles in vacuo, vacuum distillation (90° C./11 mmHg) afforded 13.5 g (83%) of butyltin trichloride as a colorless liquid. The solid material obtained from the filtration was washed twice with toluene (5 mL) and dried in vacuo to give 0.40 g of an off-white solid. The solid was dissolved in acetone-d₆ and in identified as SnCl₂ by ¹¹⁹Sn NMR (δ=−235.1). Elemental analysis: Cl, 36.92%; Sn, 62.40%. SnCl₂ requires: Cl, 87.40%; Sn, 62.60%. The results of the different experiments are presented in Table 2. TABLE 2 Results of the reaction of Bu₄Sn with SnCl₄ (1:3 molar ratio) in the presence of several catalysts.^(a) [Catalyst] Yield of BuSnCl₃ Entry Catalyst (mol %)^(b) Solvent^(c) (%)^(d) 1 Pd(PPh₃)₄ 5 toluene n.d. (47) 3 PdCl₂(PPh₃)₂ 1 no solvent n.d. (72) 4 PtCl₂(PPh₃)₂ 0.1 toluene 77 (75) 5 PtCl₂(PPh₃)₂ 0.03 toluene 87 (83) 6 — no solvent n.d. (63)^(e) 

1. Process for the production of monoalkyltin trihalides of the formula RSnX₃, wherein R=alkyl or cycloalkyl and X═Cl, Br or I, involving a redistribution reaction between tetraorganotins, triorganotin halides or diorganotin halides and tin tetrahalides, said process comprising contacting tetra-(R₄Sn), tri-(R₃SnX) or diorganotin halides (R₂SnX₂) with SnX₄ to afford said monoorganotin trihalides in the presence of at least one transition metal complex, said complex comprising at least one transition metal, M, selected from Group VIII of the periodic Table of elements, at least one monodentate ligand or bidentate ligand, L or L′, and optionally one or more anions, X, of an organic or inorganic acid, as a catalyst or catalyst precursor.
 2. Process according to claim 1, wherein the said complex has the formula L′MX₂   (I) wherein L′ is a bidentate ligand, or L₂MX₂   (II) wherein L is a monodentate ligand, or L₄M   (III) wherein L is a monodentate ligand.
 3. Process according to claim 1, wherein the said complex has the formula [L″M(μ−X)]₂   (IV) wherein L″=a cyclometallated bidentate optionally substituted o-(diarylphosphino)benzyl ligand.
 4. Process according to claim 1-3, wherein M is selected from Pt, Pd and Ni.
 5. Process according to claim 1-4, wherein X is selected from Cl, Br, I, acetate, triflate and tosylate anion.
 6. Process according to claim 1, 2, 4, or 5, wherein L is selected from phosphine, alkene, amine, organic sulfide, nitrile and imidazoline-2-ylidene.
 7. Process according to claim 1, 2 or 4-6, wherein L′ is selected from diphosphine, dialkene, diamine and bis(imidazoline-2-ylidene) ligands.
 8. Process according to claim 3, wherein L″ is an optionally substituted o-{di(2-tolyl)phosphino}benzyl.
 9. Process according to claim 1, 2 or 4-7, wherein the catalyst, catalyst precursor or catalyst system is formed by combining (I), (II) or (III) with another ligand L having the definition as given in claim
 6. 10. Process according to claim 1, 2, 4-7 or 9, wherein said monodentate ligand L is defined as a triarylphosphine, more preferably triphenylphosphine.
 11. Process according to claim 1, 2, or 4-7, wherein said bidentate ligand L′ is defined as a bidentate nitrogen ligand, more preferably N,N,N′,N′-tetramethylethylenediamine (TMEDA).
 12. Process according to claim 1-11, wherein R is selected from the group of alkyls having 1-12 carbon atoms.
 13. Process according to claim 1-12, wherein the reaction is carried out in the presence of a solvent, said solvent preferably being selected from the group of aromatic solvents, chloroaromatics, alkanes, dialkylacetamides, N-alkylpyrolidones, dialkylamides of aliphatic carboxylic acids and organic nitriles.
 14. Process according to claim 1-13, wherein M is Pt and/or Pd.
 15. Process according to claim 1-14, wherein X is Cl.
 16. Process according to claim 1-15, wherein the reaction is carried out at a temperature between 0 and 200° C.
 17. Process according to claim 1-16, wherein the reaction is carried out at a pressure between 1 and 5 bar.
 18. Process according to claim 1-17, wherein the monoalkyltin trihalide product is obtained in >60% yield (based on Sn) in less than 48 h at temperatures below 150° C.
 19. Use of a transition metal complex comprising at least one transition metal, M, selected from Group VIII of the periodic Table of elements, at least one monodentate ligand or bidentate ligand, L, L′ or L″, and optionally one or more anions, X, of an organic or inorganic acid, as a catalyst or catalyst precursor for the production of monoalkyltin trihalides of the formula RSnX₃, wherein R=alkyl or cycloalkyl and X═Cl, Br or I, using a redistribution reaction between tetraorganotins, triorganotin halides or diorganotin halides and tin tetrahalides. 